This invention is directed to a gas cooled fiber-optic cable apparatus for conveying radiant energy generated in a hostile environment to a radiation sensor located outside the hostile environment, and more particularly, it is directed to fiber-optic cable apparatus having a gas cooled radiation collecting end positioned adjacent the flame of a basic oxygen furnace (BOF) to convey radiant energy emitted from the flame to a radiation sensor located outside the hostile environment, and a method of using the conveyed radiant energy information to dynamically predict the carbon content of the steel contained in the BOF.
In the applicant's earlier U.S. Pat. No. 5,603,746 (herein incorporated in its entirety by reference), light energy emitted by the flame above the lip of a top-blown BOF is measured using a visible light sensor. The light intensity is measured as a function of the amount of oxygen blown during a heat, and three essential variables (X1, X2, and X3) that are determined in real time measurements. The values for the X1, X2, and X3 variables are used in a regression equation to calculate the carbon content of the molten steel bath during the oxygen blow that reduces the molten iron to steel. However, the 746 patent discloses sensor apparatus that is limited to measuring light emitted from an open or uncovered BOF flame, the flame being visible from almost any location along the charge and tap sides of the steelmaking shop. Such steelmaking vessels are commonly referred to as an open hood BOF, and the off-gas hood is spaced above the BOF lip leaving a large gap that provides an unobstructed view of the flame. The very visible flame makes aiming a light sensor relatively easy. For instance, during an oxygen blow, such off-gas hoods do not move downward to cover the lip of the steelmaking vessel. This provides a continuous easy line of sight that enables steelmakers to collect and measure light intensity without encountering major flame access problems. Knowing this, and taking into account the hostile environment immediately adjacent a BOF vessel, operators place light sensors at a distance of about 30 feet or more from the BOF vessel and at a height of about 5-6 feet above the operating floor of the BOF shop. At such locations, the light sensor equipment is placed in an environment where dust and fume concentrations are at a level that allows the forced air drat, disclosed in the 746 patent, to maintain a clean sighting window. This also places the sensor equipment in an ambient temperature range of about 66.degree. C. or lower, well within the range where the forced air draft can prevent the electronics from overheating.
However, new more stringent air quality regulations have made it necessary for steelmakers to install more efficient BOF off-gas hood systems. The new state-of-the-art off-gas hoods have moveable portions that completely shroud the BOF lip during the blowing cycle of the steelmaking process, and the lowered position blocks visibility or access to the BOF flame. This prevents steelmakers from using past light sensor apparatus to measure flame intensity. As a result, it has become increasingly difficult for steelmakers to determine carbon content and oxygen turn down times when the moveable hoods shroud the vessel. Additionally, in instances where BOF vessels are equipped with tap side door and heat shield structures, the enclosed vessel is almost completely hidden from the operators view during the blow cycle when the tap-side doors are closed. Such environmental enclosures block flame visibility and prevent steelmakers from using past light sensors as taught in the 746 patent. Because closed furnace structures are now in wide use throughout the steelmaking industry, it is necessary for operators to cut small open windows through either the off-gas hood or the heat shields that surround the BOF vessel, and locate their light sensor devices within several inches of the flame. The open windows provide a line of sight to the BOF flame that enables the closely placed sensors to collect radiant energy. However, such close proximity to the BOF flame is fraught with problems when steelmakers use light sensor apparatus from the past. First, the electronic circuits required to collect and convert light energy into an electrical signal overheat when placed in the high temperature zone adjacent such windows in the furnace structures. Second, if the electronics withstand the high temperature adjacent the BOF flame, the deluge of dust and fume falling on a light collector at such locations overloads the collector with dirt and reduces the accuracy of light energy readings. This results in faulty carbon analysis. And third, splashing molten slag and steel associated with the BOF steelmaking process can cover the light gathering end of the sensor, solidify, and completely destroy its ability to receive light.
In view of the above disadvantages associated with current state-of-the-art light energy analysis, a long felt need has developed within the steelmaking industry to provide an improved light sensor device that is capable of operating within the hostile environment immediately adjacent a steelmaking furnace. The improved light sensor device must be capable of operating within high temperature ranges of up to about 550.degree. C. or higher; it must be capable of repelling large amounts of dirt and fume generated by the steelmaking operation, and it must be capable of shielding its light gathering end from splashing molten steel and slag associated with the steelmaking process. The improved light sensor device must also be capable of preventing the hostile environment from damaging its sensitive electronics and light sensors that convert the light energy into an electrical signal for further processing in a programmable logic controller (PLC) to dynamically predict carbon content of the steel contained in the vessel.